The purpose of the proposed research is to investigate the structure and function of isolate and normal cowbird (Molothrus ater) song. Two methods of investigation will be used: observation of captive female cowbirds' response to various song types and description of the male cowbirds' uses of a song in a semi-natural environment. The significance of the work is that a) it represents an opportunity to explore structure-function relationships in song in a species with a different developmental history from other song birds; b) it employs a dependent variable, female response to song, that has not previously been systematically examined; c) both normal and isolate song are to be studied, a comparison typically neglected in past investigations and d) it incorporates new techniques of sound analysis that permit a more detailed acoustic description of song.